CVE-2013-1445 in PyCrypto
Summary
by MITRE
The Crypto.Random.atfork function in PyCrypto before 2.6.1 does not properly reseed the pseudo-random number generator (PRNG) before allowing a child process to access it, which makes it easier for context-dependent attackers to obtain sensitive information by leveraging a race condition in which a child process is created and accesses the PRNG within the same rate-limit period as another process.
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Analysis
by VulDB Data Team • 12/27/2024
The vulnerability identified as CVE-2013-1445 resides within the PyCrypto library's Crypto.Random.atfork function, a critical component responsible for managing cryptographic random number generation in Python applications. This flaw affects versions prior to 2.6.1 and represents a significant security weakness that undermines the integrity of cryptographic operations. The vulnerability specifically targets the pseudo-random number generator's reseeding mechanism during process forking operations, creating exploitable conditions that compromise cryptographic security.
The technical flaw manifests when a parent process creates a child process through forking operations while the Crypto.Random module is actively managing the PRNG state. The atfork function fails to properly reseed the PRNG before the child process gains access to the cryptographic random number generator, resulting in predictable or partially predictable random sequences. This occurs because both parent and child processes share the same PRNG state, and the insufficient reseeding means that the child process inherits a compromised state that may have been partially exposed through previous operations.
The operational impact of this vulnerability extends beyond simple cryptographic weakness to create substantial risks for applications relying on PyCrypto for security-sensitive operations. Context-dependent attackers can exploit this race condition by creating processes that access the PRNG within the same time window as other concurrent processes, potentially allowing them to predict or reconstruct portions of the random number sequences. This weakness directly impacts cryptographic key generation, digital signature creation, and other security protocols that depend on high-quality random numbers. The vulnerability aligns with CWE-330, which addresses the use of insufficiently random values in cryptographic contexts, and represents a clear violation of secure random number generation principles.
The attack vector leverages timing and process management characteristics to exploit the race condition inherent in the forking mechanism. Attackers can manipulate process creation timing to access the PRNG during critical periods when the random state may be partially predictable, particularly when multiple processes are created in rapid succession. This vulnerability is particularly dangerous in environments where cryptographic operations are performed under high concurrency, such as web servers or multi-threaded applications, as it can lead to the exposure of private keys, session tokens, or other sensitive cryptographic material.
Mitigation strategies for CVE-2013-1445 require immediate patching of the PyCrypto library to version 2.6.1 or later, where the atfork function properly implements PRNG reseeding. Organizations should also implement process isolation techniques and avoid relying on shared PRNG states in multi-process environments. Security teams should conduct comprehensive vulnerability assessments to identify applications using affected PyCrypto versions and ensure proper random number generation practices are implemented. The remediation aligns with ATT&CK technique T1583.001, which covers the development of tools for exploitation, as this vulnerability represents a critical weakness that attackers can leverage for cryptographic attacks and privilege escalation. Additionally, organizations should consider implementing alternative cryptographic libraries that provide better process isolation and random number generation guarantees, particularly in security-sensitive applications where predictable randomness could lead to complete system compromise.